Ultrasound imaging system apparatus and method with ADC saturation monitor

ABSTRACT

An ultrasound imaging system and method employs hardware and/or software to monitor values indicative of analog-to-digital converter (ADC) saturation for each channel as a function of depth. Any of a number of actions may be performed based on the monitored values. For example, analog amplification or TGC may be adjusted to enhance the use of a dynamic range of ADCs while reducing or eliminating ADC saturation. A TGC profile may be adjusted. An alert may be provided. A power consumption may be adjusted.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/704,397, filed on Feb. 11, 2010, now U.S. Pat. No. 8,568,319, whichis hereby incorporated herein in its entirety by reference.

BACKGROUND

Technical Field

This application relates to ultrasound imaging systems, for instancemedical ultrasound diagnostic imaging systems and, in particular, toprocessing return or echo signals in ultrasound imaging systems.

Description of the Related Art

Ultrasound imaging systems employ transducer arrays to produce andtransmit ultrasound into a body, tissue or other material. Thetransducer arrays also receive ultrasound returns or echoes and produceanalog transducer element voltage signals which are induced at thetransducer array by the received ultrasound returns or echoes.Ultrasound imaging systems typically use amplifiers to amplify theanalog transducer element voltage signals before digitization. Theanalog amplification may vary with imaging depth (i.e., time gaincompensation or control, i.e., TGC) to compensate for attenuation ofultrasound with depth.

Ultrasound imaging systems typically employ analog-to-digital converters(ADCs) to digitize the amplified analog transducer element voltagesignals. Often a separate ADC is used for each analog channel, the ADCsmapped to the transducer elements of the transducer array. Appropriatefocus delays may be applied before the digitized ADC output values fromthe channels are summed to form beams that are ultimately used toproduce image data.

To reduce system cost and power consumption, the ADCs often limit thenumber of bits (e.g., 12 bits) used to digitize the transducer elementvoltage signals. The amplifiers are typically set so that a peak signalinput to the ADC is close to a maximum range of the ADC (i.e., ADCoutput is close to a maximum possible digital value) in order to bestdiscriminate the ultrasound signal from noise and to make maximum use ofthe dynamic range of the ADC (i.e., use as many of the available digitalvalues as possible to represent the varying ultrasound signal). However,if saturation occurs (i.e., ADC values saturate at the maximum value ofADC), the ultrasound image is often significantly degraded, for exampleby distortion, artifacts, clipping, etc. Thus, the settings for theanalog amplification are typically a compromise between a costassociated with a signal that is too low (i.e., small dynamic range anddecreased signal-to-noise ratio) and the risk of encountering orexceeding a signal that is too high (e.g., clipping).

Typically, a single setting is used for the analog amplification, whichsetting must accommodate a broad variety of imaging conditions (e.g.,varying patients, different anatomy, etc.). Consequently, a significantamount of the total dynamic range is sacrificed to avoid ADC saturation.It is not possible to reliably detect saturation after summing theindividual channel contributions because it is possible, and in factlikely, that only some of the ADC channels actually saturate while otherADC channels do not. Thus, the beam sums are typically well below themaximum possible sum (i.e., maximum ADC value per channel times thenumber of channels).

New approaches that address at least some of the above describedsaturation issues are desirable.

BRIEF SUMMARY

A system and method employing hardware and/or software monitors valuesindicative of analog-to-digital converter (ADC) saturation for eachchannel as a function of depth and performs some action in response. Forexample, the system and method may adjust analog amplification or TGC inresponse to monitored values. For instance, analog amplification or TGCmay be adjusted to increase use of a dynamic range of ADCs whilereducing or eliminating ADC saturation. Also for example, an alert maybe provided to via a user interface of the ultrasound imaging system, atime gain compensation or control profile may be adjusted, and/or apower state may be changed or adjusted.

A method of operating an ultrasound imaging system may be summarized asincluding, for each of a plurality of channels of the ultrasound imagingsystem, monitoring by at least one component of the ultrasound imagingsystem at least one respective value that is indicative of ananalog-to-digital conversion saturation condition for the channel as afunction of depth; and performing at least one action at least partiallyin response to the monitoring of the at least one respective value thatis indicative of an analog-to-digital conversion saturation conditionfor the channel as a function of depth.

Performing at least one action may include for at least one of thechannels of the ultrasound imaging system, adjusting a gain of a depthdependent analog amplification of at least one return signal produced byat least one transducer element based at least in part on themonitoring.

Adjusting a gain of a depth dependent analog amplification of at leastone analog return signal may include adjusting the gain of the depthdependent analog amplification of the at least one analog return signalto at least reduce occurrences of saturation in the analog-to-digitalconversion of the at least one analog return signal.

Adjusting a gain of a depth dependent analog amplification of at leastone analog return signal may include adjusting the gain of the depthdependent analog amplification of the at least one analog return signalto prevent saturation in the analog-to-digital conversion of the atleast one analog return signal.

Adjusting a gain of a depth dependent analog amplification of at leastone analog return signal may include adjusting the gain of the depthdependent analog amplification of the at least one analog return signalto increase occurrences of saturation in the analog-to-digitalconversion of the at least one analog return signal.

Monitoring at least one respective value that is indicative of ananalog-to-digital conversion saturation condition for the channel as afunction of depth may include monitoring an analog-to-digital conversionvalue resulting from an analog-to-digital conversion for the channel asa function of depth.

Monitoring an analog-to-digital conversion value resulting from ananalog-to-digital conversion for the channel as a function of depth mayinclude, for each of a plurality of ranges of depths setting a statusbit in an analog-to-digital conversion saturation status registercorresponding to a respective one of the ranges of depths if asaturation monitoring threshold value is encountered or exceeded at therespective one of the ranges of depths for the channel.

The range of depths may be programmable, and may further includemodifying the range of depths for at least some of the channels based onat least one input received from a user.

The method may further include creating a bit mask; and applying the bitmask to selectively mask off portions of the analog-to-digitalconversion saturation status register corresponding to respective onesof a plurality of transmit focal zones.

Monitoring an analog-to-digital conversion value resulting from ananalog-to-digital conversion for the channel as a function of depth mayinclude, for each of a plurality of ranges of depths incrementing arespective counter for the respective one of the ranges of depths forthe channel each time a saturation monitoring threshold is encounteredor exceeded at the respective one of the ranges of depths for thechannel.

Monitoring an analog-to-digital conversion value resulting from ananalog-to-digital conversion for the channel as a function of depth mayinclude incrementing a respective common counter for the respective oneof the ranges of depth each time a saturation monitoring threshold isencountered or exceeded at the respective one of the ranges of depthsfor any of the channels.

The saturation threshold may be user programmable, and may furtherinclude setting the saturation monitoring threshold based on at leastone input received from a user. Monitoring an analog-to-digitalconversion value resulting from an analog-to-digital conversion for thechannel as a function of depth may include determining whether theanalog-to-digital conversion value exceeds at least one of a maximumpositive value or a maximum negative value of a respectiveanalog-to-digital converter of the channel.

The method may further include summing a number of digitized returnsignals of a plurality of channels downstream of the monitoring of theanalog-to-digital conversion value resulting from the analog-to-digitalconversion for the channel as a function of depth.

Performing at least one action may include providing an alert to via auser interface of the ultrasound imaging system. Performing at least oneaction may include adjusting a time gain control profile. Performing atleast one action may include providing a confidence metric for at leastone automated image measurement. Performing at least one action mayinclude changing a power consumption state of at least a portion of theultrasound imaging system.

The method may further include for at least some of the channels,adjusting a digital amplification of a digitized return resulting froman analog-to-digital conversion of the at least one return signal tocompensate for the adjusting of the gain of the depth dependent analogamplification.

An ultrasound system may be summarized as including an analogamplification stage operable to respectively amplify analog returnsignals produced by at least one transducer element on each of aplurality of channels of the ultrasound system; an analog-to-digitalconversion stage operable to respectively convert the amplified analogreturn signals into digital return signals on each of the plurality ofchannels of the ultrasound system; an analog-to-digital conversionsaturation monitor stage operable to monitor a respective value that isindicative of an analog-to-digital conversion saturation condition foreach of the channels as a function of depth and to perform at least oneaction in response to the monitored values; and a digital processorstage operable to process the digital ultrasound return signals.

The analog-to-digital conversion saturation monitor stage may beconfigured to respectively adjust a gain in the analog amplification ofthe analog return signals produced by the analog amplification stage oneach of the plurality of channels of the ultrasound system as a functionof depth. The analog-to-digital conversion saturation monitor stage maybe configured to adjust a gain in the analog amplification of the analogreturn signals produced by the analog amplification stage on each of theplurality of channels of the ultrasound system as a function of depth toat least reduce an occurrence of saturation of the analog-to-digitalconversion by the analog-to-digital conversion stage. Theanalog-to-digital conversion saturation monitor stage may be furtheroperable to adjust a gain in the analog amplification of the analogreturn signals produced by the analog amplification stage on each of theplurality of channels of the ultrasound system as a function of depth toincrease an occurrence of saturation of the analog-to-digital conversionby the analog-to-digital conversion stage.

The analog-to-digital conversion saturation feedback stage may befurther operable to adjust the gain in the analog amplification for therespective channels based at least in part on the detected respectivevalues.

For each of the channels the analog-to-digital conversion saturationmonitor stage may set a status bit in a respective analog-to-digitalconversion saturation status register for the channel, the status bitcorresponding to a respective one of a plurality of ranges of depths, ifa saturation monitoring threshold value is exceeded at the respectiveone of the ranges of depths for the respective channel.

The analog-to-digital conversion saturation monitor stage mayselectively mask off portions of the analog-to-digital conversionsaturation status register corresponding to respective ones of aplurality of transmit focal zones with a bit mask.

For each of the channels the analog-to-digital conversion saturationmonitor stage may increment a respective counter for a respective one ofeach of a plurality of ranges of depths each time a saturationmonitoring threshold is exceeded at the respective one of the ranges ofdepths for the respective channel.

The analog-to-digital conversion saturation monitor stage may incrementa respective common counter for the respective one of a plurality ofranges of depths each time a saturation monitoring threshold is exceededat the respective one of the ranges of depths for any of the channels.

The digital processor stage may be communicatively coupled to receive anumber of compensation signals from the analog-to-digital conversionsaturation monitor stage indicative of an amount of compensation tocompensate for the adjustment of the gain in the analog amplification ofthe analog return signals for each of the channels, and may be operableto amplify the digital return signals from the analog-to-digitalconversion stage for each of the channels based at least in part on thecompensation signals.

The analog-to-digital conversion saturation feedback stage may set asaturation monitoring threshold based on at least one input receivedfrom a user and may modify a range of depths for at least some of thechannels based on at least one input received from a user.

The analog-to-digital conversion saturation monitor stage may beconfigured to cause an alert to be provided via a user interface of theultrasound imaging system based at least in part on the monitoredvalues. The analog-to-digital conversion saturation monitor stage may beconfigured to adjust a time gain control profile based at least in parton the monitored values. The analog-to-digital conversion saturationmonitor stage may be configured to provide a confidence metric for atleast one automated image measurement based at least in part on themonitored values. The analog-to-digital conversion saturation monitorstage may be configured to at least one of entering a low power state inresponse to a lack of saturation and entering a normal power state inresponse to a saturation based at least in part on the monitored values.

A subsystem for an ultrasound imaging system may be summarized asincluding at least one saturation condition detector configured todetect an analog-to-digital conversion saturation condition as afunction of depth for at least one of each of a plurality of channels;and at least one analog amplification adjustor configured to provide atleast one adjustment signal to at least one analog amplifier, the atleast one adjustment signal indicative of an amount of adjustment in again in a depth dependent amplification of analog return signals to atleast reduce an occurrence of saturation in an analog-to-digitalconversion of the analog return signals.

The subsystem may further include at least one compensator configured toprovide at least one compensation signal to at least one digitalamplifier, which at least one compensation signal is indicative of anamount of compensation in an amplification of digitized return signalsto compensation for the amount of adjustment in gain in the depthdependent amplification of the analog return signals.

For each channel the at least one saturation condition detector may beconfigured to, for each of a plurality of ranges of depths, set a statusbit in an analog-to-digital conversion saturation status registercorresponding to a respective one of the ranges of depths if asaturation monitoring threshold value is encountered or exceeded at therespective one of the ranges of depths for the respective channel.

For each channel the at least one saturation condition detector may beconfigured to, for each of a plurality of ranges of depths, increment arespective counter for the respective one of the ranges of depths eachtime a saturation monitoring threshold is encountered or exceeded at therespective one of the ranges of depths for the respective channel.

The at least one saturation condition detector may be configured toincrement a respective common counter for the respective one of theranges of depth each time a saturation monitoring threshold isencountered or exceeded at the respective one of the ranges of depthsfor any of the channels. The subsystem may further include the analogamplifier and the digital amplifier.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not drawn to scale, and some of these elementsare arbitrarily enlarged and positioned to improve drawing legibility.Further, the particular shapes of the elements as drawn, are notintended to convey any information regarding the actual shape of theparticular elements, and have been solely selected for ease ofrecognition in the drawings.

FIG. 1 is an isometric view of an ultrasound imaging system according toone illustrated embodiment, having a handheld form factor.

FIG. 2A is a schematic diagram of a system architecture of an ultrasoundimaging system according to one illustrated embodiment.

FIG. 2B is a schematic diagram of ADC saturation monitor circuitry orfunctionality of an ultrasound imaging system according to oneillustrated embodiment.

FIG. 3 is a schematic diagram of the digital signal processing ASIC ofthe system architecture of FIG. 2A according to one illustratedembodiment.

FIG. 4 is a high level flow diagram of a method of operating anultrasound imaging system according to one illustrated embodiment.

FIG. 5 is a low level flow diagram of a method of monitoring a valueindicative of an ADC saturation condition according to one illustratedembodiment.

FIG. 6 is a low level flow diagram of a method of monitoring an ADCvalue for each channel as a function of depth using a status bitregister according to one illustrated embodiment.

FIG. 7 is a schematic diagram of a set of saturation status registersaccording to one illustrated embodiment, each saturation status registerhaving a number of bits corresponding to respective ones of a number ofranges of depths.

FIG. 8 is a graph of analog gain as a function of depth for an exemplaryoperation of an ultrasound imaging system employing 1) a saturationstatus based approach to controlling ADC saturation; and 2) employingwithout controlling ADC saturation.

FIG. 9 is a low level flow diagram of a method of monitoring an ADCvalue for each channel as a function of depth using a respective channelcounter register for each channel according to one illustratedembodiment.

FIG. 10 is a schematic diagram of a set of respective channel counterregisters according to one illustrated embodiment, each channel counterregister having a number of sets of bits corresponding to respectiveones of a number of ranges of depths to track a count for ranges ofdepths for the respective channel.

FIG. 11 is a low level flow diagram of a method of according to oneillustrated embodiment.

FIG. 12 is a schematic diagram of a common channel counter registeraccording to one illustrated embodiment, the common channel counterregister having a number of sets of bits corresponding to respectiveones of a number of ranges of depths to track a count of a number ofoccurrences of saturation for all ADCs.

FIG. 13 is a low level flow diagram of a method of adjusting an ADCsaturation condition according to one illustrated embodiment.

FIG. 14 is a low level flow diagram of a method of monitoring an ADCvalue according to one illustrated embodiment.

FIG. 15 is a low level flow diagram of a method of processing digitizedreturn or echo signals according to one illustrated embodiment.

FIG. 16 is a low level flow diagram of a method of adjusting range ofdepths according to one illustrated embodiment.

FIG. 17 is a low level flow diagram of a method of operating anultrasound imaging system employing bitmasks according to oneillustrated embodiment.

FIG. 18 is a low level flow diagram of a method of operating anultrasound imaging system including producing an alert according to oneillustrated embodiment.

FIG. 19 is a low level flow diagram of a method of operating anultrasound imaging system including adjusting a time gain compensationor control profile according to one illustrated embodiment.

FIG. 20 is a low level flow diagram of a method of operating anultrasound imaging system including adjusting a power consumption of theultrasound imaging system or portions thereof according to oneillustrated embodiment.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with ultrasound imagingsystems, microprocessors, micro-controllers, application specificintegrated circuits, transducers and displays have not been shown ordescribed in detail to avoid unnecessarily obscuring descriptions of theembodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its broadest sense, that is as meaning “and/or”unless the content clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

Various embodiments described herein employ hardware and/or software toenhance dynamic range and signal-to-noise ratio while controllingsaturation of analog-to-digital converters or an analog-to-digitalconversion function in ultrasound imaging systems. Such embodimentsmonitor values indicative of a saturation condition as a function ofdepth for each channel of an ultrasound imaging system and adjusts anamplification or gain in response to same.

In particular, the hardware and/or software may monitor an output valueof each ADC (i.e., ADC value) as a function of depth. The hardwareand/or software may, for example, set a status bit of a saturationstatus register corresponding to some range of depths for each channelif a saturation condition is encountered, met or exceeded in therespective range of depths. For example, the status bit may be set if asaturation threshold is encountered, met or exceeded. For instance, thestatus bit may be set if at least one of maximum positive or maximumnegative ADC value is encountered, met or exceeded in the respectiverange of depths. The saturation condition threshold may be programmableor user configurable. The range of depths may be programmable or userconfigurable. A register with many (e.g., 16) bits may represent a fullrange of depths for a given analog channel/ADC. Alternatively, thehardware and/or software may increment a counter every time an ADCsaturation threshold or value is encountered, met or exceeded, providingmore detailed information about a severity or frequency of a saturationcondition. Alternatively, the hardware and/or software may increment acounter corresponding to the total number of channels in saturationwithin each range of depths or depth-zone.

From time-to-time, the hardware and/or software reads the ADC saturationstatus registers or counters to analyze the ADC saturation condition asa function of depth and channel, and possibly other parameters such asray index, focal zone, and mode (e.g., 2D echo versus Doppler). Based onthe analysis, the hardware and/or software may perform any one or moreactions. For example, the hardware and/or software may adjust a timegain compensation or depth-dependent analog gain (i.e., TGC) setting tomore effectively utilize the ADC dynamic range without saturation. Thus,the hardware and/or software may for instance reduce gain at depthswhere excessive saturation is encountered, met or exceeded and possiblyincrease gain at other depths. The hardware and/or software may employan algorithm that prevents oscillation and which approaches a stableoperating point for a static imaging condition. An overall gain profilemay be maintained by adjusting or compensating a digital gain tocompensate for the adjustments made to analog gain. Also for example,the hardware and/or software may cause an alert (e.g., visual, aural,tactile) may be provided to via a user interface of the ultrasoundimaging system. Such may allow a user to make an appropriate adjust, forexample adjusting gain. As a further example, the hardware and/orsoftware may adjust a defined time gain compensation profile. As an evenfurther example, the hardware or software may be adjust a powerconsumption state of at least a portion of the ultrasound imagingsystem.

The approaches described herein may improve image quality by allowingthe ultrasound imaging system to adjust the TGC while automaticallyadapting to current imaging conditions (e.g., patient body type,anatomy, etc.), rather than accepting the limitations and compromisesrequired to accommodate a range of imaging conditions with a single TGCsetting. Such may advantageously increase dynamic range, which improvesimage contrast resolution, as well as increase signal-to-noise ratio,which provides better penetration and spatial resolution, and maysubstantially reduce the likelihood of image degradation caused bysaturation.

A number of illustrated embodiments are described below with referenceto FIGS. 1-17.

FIG. 1 shows an ultrasound imaging system 100 according to oneillustrated embodiment.

The ultrasound imaging system 100 may take the form of a portable orhandheld ultrasound imaging system. For instance, the ultrasound imagingsystem 100 include a one piece or unitary housing 102 that has an uppersection 104, a lower section 106, and a transducer array 108. The uppersection 104 may include a display 110, for example a liquid crystaldisplay (LCD). The lower section 106 may include a set of user controls112. The display 110 and user controls 112 may form all or part of auser interface. The user controls 112 may allow a user to turn theultrasound imaging system 100 ON and OFF, enter time, date, and/orpatient data, interact with a graphical user interface that includesuser selectable icons or elements of a menu (e.g., pull down menu, popupmenu), and/or select or set various operating characteristics such as anoperating mode (e.g., B mode, Doppler), color Doppler sector or framerate, and special functions. The transducer array 108 includes a set ofultrasound transducer elements which perform transformations betweenelectrical signals and ultrasound, a physical aperture, and optionally alens proximate the physical aperture. Suitable transducer arrays 108 arecommercially available from a variety of manufacturers and/or suppliers.While illustrated as a single package, an ultrasound imaging system maybe housed in two or more separate sections. Various suitable embodimentsare described in U.S. Pat. No. 7,604,596. Other configurations of theultrasound imaging system 100 may be employed.

FIG. 2A shows a system architecture 200 of an ultrasound imaging systemaccording to one illustrated embodiment.

The system architecture includes a transducer array 202,transmit/receive application specific integrated circuit (ASIC) 204,front end ASIC 206, digital signal processor (DSP) ASIC 208, and backendASIC 210, along with a number of other components and subsystems whichare discussed below. The transducer array 202, transmit/receive ASIC204, front end ASIC 206, DSP ASIC 208, backend ASIC 210, as well as thecomponents and subsystems are coupled by one or more communicationspaths or buses. For example, the transducer array 202, transmit/receiveASIC 204, front end ASIC 206, DSP ASIC 208, backend ASIC 210 may becoupled by one or more data buses, instructions buses, and/or powerbuses. Such paths or buses may take a variety of forms, includingelectrically conductive paths such as wires or electrical cables, oroptical paths such as fiber optical cable.

The transducer array 202 produces and transmits ultrasound into a body,tissue or other material. The transducer array 202 also receivesultrasound returns or echoes and produces analog transducer elementvoltage signals of analog return signal which are induced at thetransducer array by the received ultrasound returns or echoes. Thetransducer array 202 may take the form of a solid state device thatprovides electronic control capabilities, variable aperture, excellentimage performance and high reliability. The transducer array 202 may,for example, take the form of either a flat linear array or a curvedlinear array of elements. A curved linear array may provide a broadsector scanning field. The geometric curvature of a curved linear arraymay advantageously reduce steering delay requirements on a beamformer ofthe front end ASIC 206. Where the transducer array 202 takes the form ofa flat array, the beamformer functionality of the front end ASIC 206 maybe capable of producing sufficient delay to both steer and focus, forexample operating the transducer elements of the transducer array 204 asa phased array.

The transmit/receive ASIC 204 is communicatively coupled to thetransducer elements of the transducer array 202. The transmit/receiveASIC 204 drives the transducer elements. The transmit/receive ASIC 204receives representations of ultrasound returns or in the form of analogtransducer element voltage signals or analog return signals. Thetransmit/receive ASIC 204 implants an analog amplification stage,amplifying (i.e., analog amplification) the analog transducer elementvoltage signals. The analog amplification typically varies with imagingdepth (i.e., time gain compensation or TGC) to compensate forattenuation of ultrasound with depth. The transmit/receive ASIC 20 alsocontrols the active transmit and receive apertures of the transducerarray 202 and the gain of the received analog return signals or echoes.

The transmit/receive ASIC 204 may be positioned proximate the transducerarray 200, for example within inches of the elements of the transducerarray 202 to ensure short communications path. The transmit/receive ASIC204 may, for example, be positioned in the same enclosure and justbehind the transducer array 202. U.S. Pat. No. 5,893,363 titledULTRASONIC ARRAY TRANSDUCER TRANSCEIVER FOR A HANDHELD ULTRASONICDIAGNOSTIC INSTRUMENT describes a suitable transmit/receive ASIC.

The front end ASIC 206 receives the analog return signals from thetransmit/receive ASIC 204 in the form of amplified analog transducerelement voltage signals. The front end ASIC 206 beamforms the analogreturn signals from the individual elements of the transducer array 202into coherent scanline signals. For example, the front end ASIC 206includes an analog-to-digital converter (ADC) or implementsanalog-to-digital conversion 212 for each channel (only one shown),forming an analog-to-digital conversion stage which digitizes theamplified analog transducer element voltage signals and producesdigitized return signals. The front end ASIC 206 may also include delaycircuitry or implements delay functionality 214 to apply delays to thedigitized return signals. The front end ASIC 206 further includessumming circuitry or implements summing functionality 216, which sumsthe digitized return signals of the various channels.

The front end ASIC 206 also includes transmit and timing controlcircuitry or implements transmit and timing control functionality 218,providing control signals to the transmit/receive ASIC 204 to controltransmit waveform timing, aperture and focusing of the ultrasound beam.In the illustrated embodiment, the front end ASIC 206 provides timingsignals for the other ASICs and time gain control (TGC). For example,the front end ASIC 206 may include time gain control weighting factorcircuitry or implement time gain control weighting factor functionality220. The front end ASIC 206 may include digital-to-analog converter(s)or implement digital-to-analog conversion functionality 222. The frontend ASIC 206 may be communicatively coupled to a computer- orprocessor-readable storage device such as a memory 224; which storesdata used by the beamformer. U.S. Pat. No. 5,817,024 entitled HANDHELDULTRASONIC DIAGNOSTIC INSTRUMENT WITH DIGITAL BEAMFORMER and U.S. Pat.No. 5,893,363 entitled ULTRASONIC ARRAY TRANSDUCER TRANSCEIVER FOR HANDHELD ULTRASONIC DIAGNOSTIC INSTRUMENT each describe suitable front endASICS and operation.

In addition to the above described functionality, the front end ASIC 206also advantageously includes ADC saturation monitor and responsecircuitry or provides ADC saturation monitor and response functionality225 which monitors ADC saturation and responds by performing or causingperformance of one or more actions. For example, the ADC saturationmonitor and response circuitry or functionality 225 may control, preventor reduce a frequency of occurrence of ADC saturation in theanalog-to-digital conversion of the analog return signals of eachchannel as a function of depth (i.e., sample index). In particular, theADC saturation monitor and response circuitry or functionality 225 maybe configured as an analog-to-digital conversion feedback stage tomonitor values that are indicative of a ADC saturation condition foreach channel as a function of depth, and to adjust a gain in a depthdependent analog amplification in order to prevent such ADC saturationor reduce the occurrence of such ADC saturation. The ADC saturationmonitor and response circuitry or functionality 225 may be furtherconfigured to provide an adjustment or compensation in a digital gain tocompensation for the adjustment to the analog gain.

Also for example, the ADC saturation monitor and response circuitry orfunctionality 225 may additionally, or alternatively, provide one ormore signals which cause an alert to be provided via a user interface ofthe ultrasound imaging system. Such may allow a user to manually adjustvarious operational parameters, for instance analog gain. As a furtherexample, the ADC saturation monitor and response circuitry orfunctionality 225 may additionally, or alternatively, adjust a definedtime gain compensation or control profile. As an even further example,the ADC saturation monitor and response circuitry or functionality 225may additionally, or alternatively, adjust a power consumption state ofat least a portion of the ultrasound imaging system. For instance, theADC saturation monitor and response circuitry or functionality 225 maycause the ultrasound imaging system or some portion thereof to enter alow power consumption mode upon determining that no imaging is currentlybeing performed based on an absence of significant ADC saturation,particular when employing a relatively low ADC saturation threshold.

The ADC saturation monitor and response circuitry or functionality 225of the front end ASIC 206 may monitor the output (i.e., ADC values) ofthe ADC for each channel as a function of depth, updating one or moresaturation status registers or counters. The ADC saturation monitor andresponse circuitry or functionality 225 may, from time-to-time, readsaturation status information from one or more saturation statusregisters or counters to analyze an ADC saturation condition as afunction of depth, possibly as a function of channel, and/or possibly asa function of other parameters such as ray index, focal zone, and/ormode (e.g., 2D echo; Doppler). The ADC saturation monitor and responsecircuitry or functionality 225 may adjust analog amplification or TGCbased on such information to increase or enhance utilization of adynamic range of the ADC(s) where possible, while avoiding saturation.Thus, analog gain may be reduced at depths where excessive saturation isencountered, met or exceeded. Analog gain may be increased where doingso will not cause excessive saturation. The ADC saturation monitor andresponse circuitry or functionality 225 should accomplish such controlwhile preventing unnecessary oscillation. For instance, the ADCsaturation monitor and response circuitry or functionality 225 mayemploy a feedback mechanism such as digital filter function to achievestability. The ADC saturation monitor and response circuitry orfunctionality 225 may advantageously employ even more sophisticatedapproaches that rely on saturation information accumulated over time,for instance adaptive filters (e.g., data dependent).

As best illustrated in FIG. 2B, the ADC saturation monitor and responsecircuitry or functionality 225 includes one or more saturation conditiondetectors, which may take the form of one or more comparators or mayimplement a comparison functionality 226 ₁-226 _(N) (collectively 226).The comparators or comparison functionality 226 may compare the outputof respective ADCs or ADC values to one or more threshold values todetermine whether an ADC saturation condition has been encountered, metor exceeded. The threshold value(s) may be stored in a computer- orprocessor-readable saturation condition threshold storage medium 223.Such threshold value(s) may be user configurable, for instance by userinput received via the user controls. Alternatively, the thresholdvalue(s) may be preset, for example by the manufacturer of theultrasound imaging system. Default threshold value(s) may be defined.Threshold values may, for example, be logically associated withdifferent operational modes.

The saturation condition detectors may detect a variety of events orconditions, based on the particular threshold values. For instance, thethreshold values may be set such that the saturation condition detectorsdetect actual saturation of the respective ADCs. Alternatively, thethreshold values may be set such that the saturation condition detectorsdetect an approach to an actual saturation of the respective ADCs.Alternatively, the threshold values may be set such that the saturationcondition detectors detect non-saturation of the ADCs. For instance, thethreshold may be set well below a value at which saturation of the ADCsoccurs. Such may indicate that the analog amplification or gain is toolow and should be adjusted upwards to increase or maximize use of theavailable dynamic range of the ADCs. Such may also indicate that imagingis not currently being performed, allowing the ultrasound imaging systemor some portions thereof to enter into a power saving, low powerconsumption mode.

Multiple threshold values may be employed, for example a relativelyhigher set of values indicative of saturation actually occurring orabout to occur, and a relatively lower set of values indicative of alack of actual saturation and hence a failure to use the desired expanseof the dynamic range of the ADCs. Thus, analog amplification or gain maybe increased in response to detection of values at or exceeding therelatively higher set of threshold values, and decreased in response todetection of values at or below the relatively lower set of thresholdvalues. Such may advantageously enhance use of ADC dynamic range.

The ADC saturation monitor and response circuitry or functionality 225may include a register(s) updater or implement registers(s) updatefunction 227. The register(s) updater or registers(s) update function227 updates one or more saturation condition registers or counters 228to reflect the outcome of the comparisons. For example, the register(s)updater or update function 227 may set a respective bit of a saturationstatus register 228 if a saturation condition is encountered, met,exceeded or occurs at a respective range of depths for a respectivechannel. For instance, a saturation status register 228 with a setnumber of bits (e.g., 16 bits) may be used to represent a full range ofdepths for a given analog channel or ADC. Also for example, theregister(s) updater or update function 227 may increment a respectivecounter 228 if a saturation condition is encountered, met, exceeded, oroccurs at a respective range of depths for a respective channel. As afurther example, the register(s) updater or update function 227 mayincrement a common channel counter 228 for a range of depths if asaturation condition is encountered, met, exceeded, or occurs at arespective range of depths for any of the channels. The denomination“common” as used in reference to a common channel counter means that thecounter is common to or tracks the status for more than one channel.

The ADC saturation monitor and response circuitry or functionality 225may include a register(s) clearer or implement a clear register(s)function 229. The register(s) clearer or clear register(s) function 229may clear the saturation condition register(s) or counter(s) fromtime-to-time. Such may occur periodically, for example in response to asignal from a timer, clock or counter 230. Alternatively oradditionally, such may occur non-periodically. For example, theregister(s) clearer or clear register(s) function 229 may clear one ormore saturation condition registers or counters in response to anoccurrence of an event or condition. For instance, the register(s)clearer or clear register(s) function 229 may clear one or moresaturation condition registers or counters in response to an adjustmentof analog amplification of gain for the channel(s) and/or range ofdepths.

The ADC saturation monitor and response circuitry or functionality 225may include an analog amplification or gain adjuster or implement ananalog amplification or gain adjuster function 231. The analogamplification or gain adjuster or analog gain adjuster function 231determines an amount of adjustment to be made to the analogamplification or gain for each channel as a function of depth. Such maybe to prevent or reduce saturation of the respective ADC, and producessignals which cause the determined adjustments in the analog gain oramplification. For example, the analog amplification or gain adjustor oranalog amplification or gain adjustor function 231 may determine anamount of adjustment that is sufficient to prevent or reduce the ofoccurrence of saturation of the ADC for each channel as a function ofdepth. The analog gain amplification or adjustor or analog amplificationor gain adjustor function 231 may provide appropriate controls signalsto the transmit/receive ASIC 204 to implement the determined adjustment.Such may also be used to increase saturation to some nominal level,which may ensure that the analog amplification or gain has not beenadjusted too low. Such may also be used to determine an activity levelof the ultrasound imaging system, allowing entry into an energy savingor a low power consumption state.

The ADC saturation monitor and response circuitry or functionality 225may optionally include compensation circuitry or implement acompensation functionality 232 that causes an adjustment or compensationin a digital gain or amplification to compensate for the analog gain oramplification adjustments. For example, the compensation circuitry orcompensation functionality 232 may determine an amount of adjustment orcompensation to be made in the gain or amplification of the digitalreturn signal to at least partially offset for the adjustment made inthe amplification of the analog return signal. The compensationcircuitry or compensation functionality 232 may provide one or moresignals to the DSP ASIC 208 indicative of a determined adjustment orcompensation to be made in the digital gain or amplification tocompensate for the adjustment to the analog amplification.

Various approaches may be employed in implementing the ADC saturationcontrol functionality. For example, a saturation status approach may beemployed which tracks a saturation status (i.e., has a saturationcondition occurred) for each of a number of ranges of depths for eachchannel. Also for example, a respective channel counter approach may beemployed which tracks a total number of times a saturation condition hasoccurred for each of a number of ranges of depths for each channel. As afurther example, a common channel counter approach may be employed whichtracks a total number of times a saturation condition has occurred foreach of a number of ranges of depths for any of the channels. Theseapproaches are discussed in more detail below in reference to variousmethods of operating the ultrasound imaging system architecture 200.

Returning to FIG. 2A, the DSP ASIC 208 acts as a digital processorstage, receiving beamformed scanline signals from the front end ASIC 206and processing the same. The DSP ASIC 208 filters the scanline signals,amplifies the scanline signals and processes the filtered scanlinesignals as B mode signals, Doppler signals, or both. For example, DSPASIC 208 includes circuitry or implements one or more filters (notshown) and one or more amplifiers or implements an amplificationfunctionality 233.

In some embodiments, the DSP ASIC 208 may provide several advancedfeatures including synthetic aperture formation, frequency compounding,Doppler processing such as power Doppler (e.g., color flow or colorpower) processing, and speckle reduction as more fully detailed below.For example, the DSP ASIC 208 may include appropriate circuitry for ormay implement a synthetic aperture functionality 234, a frequencycompounding functionality 236, and/or Doppler processing functionality238 to perform power Doppler processing. The DSP ASIC 208 may becommunicatively coupled to a computer- or processor-readable storagedevice such as 3D CPA memory 240 to provide storage used in threedimensional power Doppler (3D CPA) imaging.

The back end ASIC 210 receives the ultrasound B mode and Dopplerinformation from the DSP ASIC 208. The back end ASIC 210 implements ascan conversion 242 that performs scan conversion and produces videooutput signals or frames of video 244. The back end ASIC 210 may beconfigured to add alphanumeric information to the display such as thetime and/or date via a time and/or date function 246, and patientidentification. A graphics processor 248 may overlay the ultrasoundimages with information such as depth and focus markers and cursors.Frames of ultrasonic images 244 may be stored in a video memory 250communicatively coupled to the back end ASIC 210. Such may allowselected frames to be recalled and replayed, for instance in a liveCineloop® real-time sequence. Video information may be available at avideo output. The video information may be made available in a varietyof formats, for instance NTSC and PAL formats or RGB drive signals foran integral display 252 or other a video monitor.

The back end ASIC 210 includes a central processor 254, for example areduced instruction set controller (RISC) or other microprocessor orcontroller. The central processor 254 may execute instructions and/orprogram data stored on one or more computer- or processor-readablestorage devices, for example a program memory 256.

The central processor 254 is communicatively coupled to the front endASIC 206 and DSP ASIC 210 to control and synchronize the processing andcontrol functions throughout the ultrasound imaging system architecture200. For example, the central processor 254 may coordinate processtiming and loading of buffers and registers with the data necessary toperform the processing and display requested by the user. Timing for thecentral processor 254 is provided by clock signals from the clockgenerator, which may be located on or implemented by the front end ASIC206.

The central processor 254 is operated under user control by commands,selections and/or entries made by the user via the user controls 260. Asdescribed above, the user controls 260 allow a user to direct andcontrol the operations of the ultrasound imaging system architecture200. Where a handheld form factor is employed, a number of functions,such as patient data entry, Cineloop® operation, and 3D review, may beoperated through menu control provided via a graphical user interface.Such may advantageously minimize the number of keys, buttons or switchespresent on a small handheld housing. Additionally, or alternatively, anumber of operational functions may be programmed to be logicallyassociated with specific diagnostic applications. Such operationalfunctions may be automatically executed or performed when a specificoperating mode or application is selected by a user. For example,selection of B mode imaging may automatically invoke frequencycompounding and depth dependent filtering on the DSP ASIC 208, whileselection of Doppler operation may cause automatic set up of a fourmultiplier filter as a wall filter on the DSP ASIC 208. The menuselection of specific clinical applications can, for example,automatically invoke specific feature settings such as TGC controlcharacteristics and focal zones.

The central processor 254 may be communicatively coupled to acommunications port (e.g., Universal Serial Bus or USB port, Ethernetport, FIREWIRE® port, infrared transmitter/receiver) 258. Thecommunications port 258 allows other modules and functions to becommunicatively coupled to or communicate with the ultrasound device.The communications port 258 can communicatively couple to a modem orcommunications link to transmit and receive ultrasound images,ultrasound information and/or other information from remote locations.The communications port 258 can accept other data storage devices to addnew functionality to the ultrasound device, for instance an ultrasoundinformation analysis package. The communications port 258 may also allowthe processor 254 to access additional program instructions or dataand/or transmit image information remotely.

A power and battery management subsystem 262 applies battery power tothe other components and subsystems of the ultrasound imaging system.For example, the power and battery management subsystem 262 may monitorand control electrical power applied to the transducer array 202,thereby controlling the acoustic energy which is applied to the patient.The power subsystem 262 may also be configured to minimize overall powerconsumption of the ultrasound imaging system. The power subsystem 262may provide electrical power from a portable power storage device (e.g.,rechargeable battery cells, ultra-capacitor array, fuel cell array),particularly where the ultrasound imaging system takes the form of ahandheld or portable device. The power subsystem 262 may include a DC-DCconverter to convert the low battery voltage to a higher voltage whichis applied to the transmit/receive ASIC 204 to drive the elements of thetransducer array 202. The power subsystem 262 may include a rectifierand step down converter to convert AC power to recharge the powerstorage device (e.g., rechargeable battery cells, ultra-capacitorarray).

While the various components are generally described above as beinghoused in a single unitary or single piece housing, other alternativeswill be readily apparent from this description. For instance, the frontend ASIC 206, the DSP ASIC 208, and the back end ASIC 210 could belocated in a common enclosure, with the beamformer of the front end ASIC206 physically and/or communicatively detachably coupled to the elementsof the transducer array 202. This allows different transducer arrays tobe used with the digital beamformer, digital filter, and image processorfor various diagnostic imaging procedures. The display 252 could belocated in the same enclosure as the front end, DSP and back end ASICs,or the output of the back end ASIC 210 could be connected to a separatedisplay device. Alternatively, the transducer array 202,transmit/receive ASIC 204 and front end ASIC 206 could be housed in atransducer housing, with the DSP ASIC 208, back end ASPIC 210, usercontrols 260 and display 252 housed in a separate housing. Othervariations are possible.

FIG. 3 shows a DSP ASIC 300 according to one illustrated embodiment. TheDSP ASIC 300 may be used to implement the DSP ASIC 208 (FIG. 2A).

The DSP ASIC 300 includes normalization circuitry or implements anormalization functionality 302 which receives scanline signals from afront end ASIC, for example front end ASIC 206 (FIG. 2A). Thenormalization circuitry or functionality 302 multiplies the receivedscanline signals by a variable coefficient stored in a coefficientmemory 304 to normalize the received signals for aperture variation.

The ultrasound imaging system may be operated in the B mode to form astructural image of tissue and organs or may be operated to processDoppler echo signals for power Doppler (CPA) display The DSP ASIC 300may include a first four multiplier filter 306, a multiplexer 308, and asecond four multiplier filter 310. Each of the four multiplier filters306, 310 includes a multiplier and an accumulator which operate as afinite impulse response (FIR) filter. The four multiplier filters 306,310 may perform decimation band pass filtering, and may reduce radiofrequency (R.F.) noise and quantization noise through bandwidth limitingeffects. I and Q return or echo signal samples are produced at theoutputs of filters 306 and 310, amplified if desired by the multipliersof gain stages 312, 314, then stored in the R.F. memory 316. The Qsamples are coupled to the R.F. memory 316 by a multiplexer 318.

A compression circuit 322 includes two shift registers and a multiplierarranged to form a CORDIC processor for performing envelope detection.The detected signal is compressed and scaled to map the detected signalsto a desired range of display gray levels.

A FIR filter 324 may perform low pass filtering of the grayscalesignals. If the selected scanning mode utilizes a single transmit focalpoint, the grayscale signals are transmitted to the back end ASIC 210(FIG. 2A) for scan conversion. Prior to leaving the DSP ASIC 300, thegrayscale signals can be frame averaged by an infinite impulse response(IIR) filter 328 which utilizes image frame memory 326 as a frame bufferand incorporates one multiplier and two adders 320 to perform frame toframe averaging.

The user may choose to process the grayscale image with certain imageenhancement features, such as depth dependent filtering or specklereduction such as the frequency compounding technique described in U.S.Pat. No. 4,561,019.

The DSP ASIC 300 may also include a flash suppression processor 330which may operate by any of a number of known flash suppressiontechniques, such as frame to frame comparison and elimination or thenotch filtering technique of U.S. Pat. No. 5,197,477. One suitabletechnique for flash suppression processing is min-max filtering asdescribed in detail in the parent, U.S. Pat. No. 5,722,412.

The sequences of operating the DSP ASIC 300 for B mode (two dimensional)echo and Doppler processing, respectively, are described in more detailin flowcharts of FIGS. 6 and 7, respectively, of U.S. Pat. No.7,604,596.

The image frame memory 326 and its associated flash suppressionprocessor 330 and IIR filter 328 can be located on the back end ASIC 210(FIG. 2A), thereby partitioning the DSP ASIC 300 and the back end ASIC210 (FIG. 2A) at the output of FIR filter 324. Thus, the digital signalprocessing function of FIG. 3 up through the output of FIR filter 324,or all of the functions shown in FIG. 3 can be fabricated on a singleintegrated circuit chip, depending upon this partitioning choice andother integrated circuit layout considerations.

FIG. 4 shows a high level method 400 of operating an ultrasound imagingsystem, according to one illustrated embodiment. The method 400 focuseson aspects of the operation related to ADC saturation control, and inthe interest of clarity and brevity omits many general details ofoperation that are set out in other descriptions of ultrasound imagingsystem, for instance U.S. Pat. No. 7,604,596. The method 400 isdiscussed with reference to FIGS. 2A and 2B.

At 402, the ultrasound imaging system transmits ultrasound into amedium, for example into bodily tissue. In particular, thetransmit/receive ASIC 204 (FIG. 2A) may cause the transducer elements ofthe transducer array 202 to transmit ultrasound in response to controlby the front end ASIC 206, DSP ASIC 208 and the central processor 254 ofthe back end ASIC 210. Also as previously explained, for exampleoperating the transducer elements as a phased array.

At 404, the ultrasound imaging system receives return or echoultrasound. In particular, the transducer elements of the transducerarray 202 (FIG. 2A) may receive returned or echo ultrasound from thebody, tissue or other material. The transducer elements transform suchinto analog return signals, which may be electrical signals having avoltages corresponding to a magnitude of the return or echo ultrasound.The transducer array 202 (FIG. 2A) may provide the analog return signalsto the transmit/receive ASIC 204.

At 406, the ultrasound imaging system amplifies the analog returnsignals. In particular, the transmit/receive ASIC 204 (FIG. 2A) mayamplify the analog return signals received from the transducer elementsof the transducer array 202. As described herein, a gain inamplification of the analog signals may be adjusted to control ADCsaturation.

At 408, the ultrasound imaging system performs analog-to-digitalconversion on the analog return signals. In particular, for each channela respective ADC 212 (FIG. 2A) of the front end ASIC 206 converts theanalog return signals to digitized or sampled return signals. Aspreviously explained, analog-to-digital conversion may result inclipping if saturation is not adequately controlled.

At 410, for each channel, the ultrasound imaging system monitors a valuethat indicative of an ADC saturation condition as a function of depth.For example, a comparator or comparison function 226 of the front endASIC 206 may monitor for the occurrence of an ADC saturation conditionas a function of depth. In particular, the comparator or comparisonfunction 226 ₁-226 _(N) (FIG. 2B) of the front end ASIC 206 (FIG. 2A)may compare a value with a saturation condition threshold, determiningwhen the saturation condition threshold is encountered, met or exceeded.The comparison may include comparing to both a maximum positivesaturation condition threshold and a maximum negative saturationcondition threshold. The saturation condition threshold may be set suchthat encountering, meeting or exceeding the saturation conditionthreshold is indicative of saturation actually occurring. Alternatively,the saturation condition threshold may be set such that encountering,meeting or exceeding the threshold is indicative of approaching or beingwithin some amount or percentage of saturation occurring. The results ofthe comparison may be saved, for example to a saturation conditionregister or counter. For instance, if a saturation condition isencountered, met or exceeded, a status bit may be set or a counter maybe incremented. The monitoring 410 may be continuous or periodic duringthe operation of the ultrasound imaging system, or may be non-periodic.While illustrated as monitoring values downstream or afteranalog-to-digital conversion, some embodiments may monitor valuesupstream of or before the analog-to-digital conversion. For example, theultrasound imaging system may monitor a magnitude of a voltage of theanalog return signals provided from the transmit/receive ASIC 204 beforedigitization or sampling by the ADCs.

At 412, for at least one of the channels of the ultrasound imagingsystem, adjusts a gain of a depth dependent analog amplification of atleast one analog return signal produced by at least one transducerelement based at least in part on the monitoring to prevent saturationin the analog-to-digital conversion of the at least one analog returnsignal. In particular, an analog gain adjustor or analog gain adjustorfunctionality 231 (FIG. 2B) of the front end ASIC 206 (FIG. 2A) maydetermine an amount of adjustment, and may provide a correspondingsignal to the transmit/receive ASIC 204 to adjust the gain oramplification of the analog return signals. The adjustment may, forexample, be linear or may be non-linear. The adjustment may ensure thatclipping does not occur, or may only reduce the probability or frequencyof clipping occurring. The analog gain adjustor or analog gain adjustorfunction 231 may employ one or more saturation condition registers orcounters 231 FIG. 2B) to determine which channels to adjust, and todetermine the amount or level of adjustment. The registers or counters231 may, for example, be cleared or reset after adjustment. Theadjusting 412 may be continuous or periodic, or may occurnon-periodically. The adjusting 412 may run or be executed in parallelwith the monitoring 410, for example as separate threads in amulti-threaded process.

Optionally at 414, for at least some of the channels, the ultrasoundimaging system adjusts a digital amplification of a digital returnsignal resulting from an analog-to-digital conversion of the at leastone analog return signal to compensate for the adjusting of the gain ofthe depth dependent analog amplification. In particular, a compensationcircuitry or compensation functionality 232 (FIG. 2B) of the front endASIC 206 (FIG. 2A) may determine an amount of adjustment and provide acorresponding signal to the DSP ASIC 208 to adjust the gain produced byamplification of the digitized return signals. The adjustment orcompensation may, for example be linear, or may be non-linear. Theadjustment or compensation may completely or fully compensate for theadjustment in the analog amplification or gain, or may only partiallycompensate for the adjustment in the analog amplification or gain.

Optionally at 414, the ultrasound imaging system further processes thedigitized return signals. For example, the DSP ASIC 208 may sum thedigital return signals of a plurality of channels. Such summing mayoccur downstream of the monitoring of the analog-to-digital conversionvalue resulting from the analog-to-digital conversion for the channel asa function of depth.

FIG. 5 shows a method 500 of monitoring a value indicative of an ADCsaturation condition according to one illustrated embodiment. The method500 may be useful in performing the monitoring of values indicative anADC saturation condition 410 of the method 400 (FIG. 4).

At 502, the ultrasound imaging system monitors ADC values resulting fromanalog-to-digital conversion for a channel as a function of depth. Inparticular, the front end ASIC 206 may monitor the magnitude ofdigitized return signals from respective ones of the ADCs 212 (FIG. 2A).As described herein, monitoring may include comparing a magnitude of thedigitized return signals to a saturation condition threshold.

FIG. 6 shows a method 600 of monitoring an ADC value for each channel asa function of depth using a status bit register according to oneillustrated embodiment. The method 600 may be useful in performing themonitoring of ADC values for each channel as a function of depth 502 ofthe method 500 (FIG. 5).

At 602, for each of a plurality of ranges of depths, the ultrasoundimaging system sets a respective status bit in ADC saturation statusregister if saturation monitoring threshold value is encountered, met orexceeded at the respective range of depths for the channel. Thesaturation status registers may be cleared from time-to-time, forinstance periodically or non-periodically, for instance in response tothe occurrence of an event. For example, a saturation status registermay have all bits cleared (e.g., 0). Then selected bits in the registercorresponding to certain ranges of depths are set (e.g., 1) if asaturation condition is encountered, met or exceeded at the respectiverange of depth. Later the bits of the register may again be cleared.

FIG. 7 shows a set of saturation status registers 700 a-700 n(collectively 700) according to one illustrated embodiment. Thesaturation status registers 700 may be employed with a saturation statusapproach to implementing ADC saturation control, for instance the method600 (FIG. 6).

The ultrasound imaging system may, for example, employ a respectivesaturation status register 700 a-700 n for each channel. Each register700 a-700 n may have a number of bits 702 a-702 h (collectively 702,only two called out for one saturation status register in FIG. 7), eachbit 702 assigned to carry a saturation status (e.g., Boolean values0, 1) that indicates a saturation condition of a respective one of eachof a number of respective ranges of depths for the channel. Thus, forexample, for any given channel, any ranges of depths in which thesaturation condition was encountered, met or exceeded may have a value 1stored in the corresponding bit of the corresponding one of thesaturation status registers 700. Other bits may have a value 0 storedtherein, indicating that the saturation condition was not encountered,met or exceeded at the corresponding ranges of depths.

FIG. 8 shows analog gain as a function of depth for an exemplaryoperation of an ultrasound imaging system employing 1) a saturationstatus based approach 802 to controlling ADC saturation; and 2) withoutcontrolling ADC saturation 800.

In particular, a first curve 900 shows the analog TGC as a function ofdepth without control of the ADC saturation. A second curve 902 showsanalog TGC gain as a function of depth while controlling ADC saturationusing a saturation status based approach, such as that of the method 600(FIG. 6).

FIG. 9 shows a method 900 of monitoring an ADC value for each channel asa function of depth using a respective channel counter register for eachchannel according to one illustrated embodiment. The method 900 may beuseful in performing the monitoring of ADC values for each channel as afunction of depth 502 of the method 500 (FIG. 5).

At 902, for each channel and for each of a plurality of ranges of depthsfor that channel, the ultrasound imaging system increments a respectivecounter for the range of depths for the respective channel each time asaturation monitoring threshold is encountered, met or exceeded at therespective range of depths for the channel. In particular, theregister(s) updater or update functionality 227 (FIG. 2B) may incrementa counter for each range of depths for each channel each time asaturation condition is encountered, met or exceeded on that channel forthat respective range of depth. The counters may be reset fromtime-to-time, for example periodically or in response to an occurrenceof an event. The event may, for instance, be the adjustment of theanalog amplification or gain, or some other event.

FIG. 10 shows a set of counters in the form of respective channelcounter registers 1000 a-1000 n (collectively 1000) according to oneillustrated embodiment. The respective channel counter registers 1000may be employed with a respective channel counter approach toimplementing ADC saturation control, for instance the method 900 (FIG.9).

The ultrasound imaging system may, for example, employ respectiveregisters 1000 a-1000 n, one for each channel. Each register 1000 a-1000n may have a number of sets of bits 1002 a-1002 h (collectively 1002,only two called out for one register in FIG. 10), each set of bits 1002assigned to carry a count that indicates a total number of times that asaturation condition has been encountered, met or exceeded for arespective one of each of a number of respective ranges of depths forthe channel since the counter was last reset. Thus, for example, for anygiven channel, any ranges of depths in which a saturation condition hasnot been encountered, met or exceeded may store or contain a value 0 inthe respective set of bits. Any ranges of depths in which a saturationcondition has been encountered, met or exceeded once may store a value1, encountered, met or exceeded twice may store a value 2, and so on aslimited by the size of the register or counter. The channel counterregister may be reset from time-to-time, for example periodically or inresponse to an occurrence of an event. The event may, for instance, bethe adjustment of the analog amplification or gain, or some other event.A flag or other mechanism may be employed to monitor any occurrences ofexceeding a limit (e.g., overflow) of the respective channel counter.

FIG. 11 shows a method 1100 of monitoring an ADC value for each channelas a function of depth using a common channel counter register which iscommon to each channel according to one illustrated embodiment. Themethod 1100 may be useful in performing the monitoring of ADC values foreach channel as a function of depth 502 of the method 500 (FIG. 5).

At 1102, the ultrasound imaging system increments a count in the commonchannel counter register for the respective range of depth each timesaturation monitoring threshold is encountered, met or exceeded at therespective range of depths for any of the channels. In particular, theregister(s) updater or update functionality 227 (FIG. 2B) may incrementa counter for each range of depths each time a saturation condition isencountered, met or exceeded on any one of the channels for thatrespective range of depth. The common channel counter register may bereset from time-to-time, for example periodically or in response to anoccurrence of an event. The event may, for instance, be the adjustmentof the analog amplification or gain, or some other event.

FIG. 12 shows a common channel counter in the form of a common channelcounter register 1200, according to one illustrated embodiment. Thecommon channel counter register 1200 may be employed with a respectivecommon channel counter approach to implementing ADC saturation control,for instance the method 1100 (FIG. 11).

The common channel counter register 1200 may include a number of sets ofbits 1202 a-1202 h, each set of bits 1202 assigned to carry a count thatindicates a total number of times that a saturation condition has beenencountered, met or exceeded for a respective one of each of a number ofranges of depths for any of the channels. Thus, for example, any rangesof depths in which a saturation condition has not been encountered, metor exceeded for any channel may store a value 0 in the respective set ofbits. Any ranges of depths in which a saturation condition has beenencountered, met or exceeded once for any of the channels may store avalue 1, encountered, met or exceeded twice for any of the channels maystore a value 2, and so on as limited by the size of the common channelcounter register or other counter. A flag or other mechanism may beemployed to monitor any occurrences of exceeding a limit (e.g.,overflow) of the common channel counter.

FIG. 13 shows a method 1300 of adjusting an ADC saturation condition,according to one illustrated embodiment. The method 1300 may, forexample, be employed as an additional act in performing the method 400(FIG. 4).

At 1302, the ultrasound imaging system sets a saturation monitoringthreshold based at least on one input received from a user. For example,user input may be received by the central processor 254 (FIG. 2A) viathe user controls 260. The central processor 254 may provide appropriatesignals to the front end ASIC 206 to set the saturation monitoringthreshold. For example, the signals may specify a positive and/or anegative saturation condition threshold value. The ultrasound imagingsystem may additionally, or alternatively, employ a default saturationmonitoring threshold, for instance a maximum positive and/or maximumnegative value for the ADC.

FIG. 14 shows a method 1400 of monitoring an ADC value, according to oneillustrated embodiment. The method 1400 may be employed in performingthe monitoring of ADC values for a channel as a function of depth 502 ofthe method 500 (FIG. 5).

At 1402, the ultrasound imaging system determines whether an ADC valueproduced by an ADC of a channel exceeds at least one of a maximumpositive value or a maximum negative value. The maximum positive and/ormaximum negative values may, for example, be predefined by amanufacturer of the ultrasound imaging system. The maximum positiveand/or maximum negative values may be default values which arechangeable by a user. Alternatively, maximum positive and/or maximumnegative values may be fixed values.

FIG. 15 shows a method 1500 of processing digitized return signals,according to one illustrated embodiment. The method 1500 may be employedin performing the further processing of digitized return signals 416 ofthe method 400 (FIG. 4).

At 1502, the ultrasound imaging system sums the digitized return signalsof a plurality of channels. The summation is performed downstream of themonitoring of the ADC channels. In particular, the summer or summingfunction 216 (FIG. 2A) of the front end ASIC 206 may sum the digitizedreturn signals of the various channels. Notably, monitoring of ADCsaturation conditions upstream of the summing permits saturationconditions occurring on individual channels to be detected before suchchannel specific information is lost in the summing of the digitizedreturn signals from various channels.

FIG. 16 shows a method 1600 of adjusting range of depths, according toone illustrated embodiment. The method 1600 may be employed as anadditional act in performing the method 400 (FIG. 4).

At 1602, the ultrasound imaging system modifies a range of depths for atleast some of the channels. The modification may be in response to oneor more user inputs. For example, user input may be received by thecentral processor 254 (FIG. 2A) via the user controls 260. The centralprocessor 254 may provide appropriate signals to the front end ASIC 206to set the range of depths. For example, the signals may specify a newrange of depths. The ultrasound imaging system may additionally, oralternatively employ a default set of ranges of depths.

FIG. 17 shows a method 1700 of operating an ultrasound imaging systememploying bitmasks according to one illustrated embodiment. The method1700 may be employed as an additional act in performing the method 400(FIG. 4).

The ultrasound imaging system may provide the ability to control the ADCsaturation control functionality. For example, the ultrasound imagingsystem may provide a user with the ability to 1) enable or start, 2)disable or stop, and/or 3) clear or reset the ADC saturation controlfunctionality. In particular, the ultrasound imaging system may allowthese operations to be performed using a bit mask so that activedepth-bits can be varied by transmit focal zones.

At 1702, the ultrasound imaging system creates a bit mask. At 1704, theultrasound imaging system applies the bit mask to selectively mask offportions of ADC saturation status register corresponding to respectiveones of a number of transmit focal zones.

For example, a bit mask 11110000 may be created, which during a zone 1acquisition is applied to enable bits corresponding to a first transmitfocal zone while disabling bits corresponding to a second transmit focalzone. Alternatively, a bit mask 00001111 may be created, which isapplied during zone 2 acquisition to disable bits corresponding to afirst transmit focal zone while enabling bits corresponding to a secondtransmit focal zone.

FIG. 18 shows a method 1800 of operating an ultrasound imaging systemaccording to one illustrated embodiment. The method 1800 may be used aspart of, or in addition to the method 400 (FIG. 4), for instance beingexecuted or performed in response to monitoring of values 410.

At 1802, the monitoring and response circuitry or functionality may senda signal to cause an alert. For example, the monitoring and responsecircuitry or functionality may send a sign to the central processor tocause one or more components of the user interface to produce an alert(e.g., visual, aural and/or tactile).

At 1804, one or more components of the user interface (e.g., display,speaker, vibrator) produces an alert. The alert may allow a user tomanual change one or more of the operational settings of the ultrasoundimaging system, for instance the analog amplification or gain, or someother operation setting for instance the mode.

FIG. 19 shows a method 1900 of operating an ultrasound imaging systemaccording to one illustrated embodiment. The method 1900 may be used aspart of, or in addition to the method 400 (FIG. 4), for instance beingexecuted or performed in response to monitoring of values 410.

At 1902, the monitoring and response circuitry or functionality mayadjust a time gain compensation or control profile. Such may be adjustedbased on the magnitude and/or frequency of detected values exceeding thethresholds. The time gain compensation or control profile may beadjusted upwards, as well as downwards, depending on a desired result.

FIG. 20 shows a method 2000 of operating an ultrasound imaging systemaccording to one illustrated embodiment. The method 2000 may be used aspart of, or in addition to the method 400 (FIG. 4), for instance beingexecuted or performed in response to monitoring of values 410.

At 2002, the monitoring and response circuitry or functionality mayadjust a power consumption of the ultrasound imaging system or one ormore portions thereof. For example, the monitoring and responsecircuitry or functionality may cause the ultrasound imaging system orone or more components thereof to enter a power savings or low powermode. Such may be in response to determining that there is a lack ofsaturation occurring, indicating that no imaging is currently occurring.A relatively low threshold condition may be set to detect such acondition. Additionally, or alternatively, the monitoring and responsecircuitry or functionality may cause the ultrasound imaging system orone or more components thereof to enter a normal operation or regular orhigh power mode. Such may be in response to determining that there issome nominal level of saturation occurring, indicating that imaging iscurrently occurring. The nominal level may be below some upper level atwhich saturation occurs too frequently but which may also be above somelower level at which sufficient use of the dynamic gain of the ADCs isnot occurring. Such may advantageously allows power conservation whilestill increasing the use of the dynamic range of the ADCs.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other ultrasound systems, notnecessarily the exemplary ultrasound imaging system generally describedabove.

For instance, the foregoing detailed description has set forth variousembodiments of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one embodiment, the present subject matter may beimplemented via Application Specific Integrated Circuits (ASICs).However, those skilled in the art will recognize that the embodimentsdisclosed herein, in whole or in part, can be equivalently implementedin standard integrated circuits, as one or more computer programsexecuted by one or more computers (e.g., as one or more programs runningon one or more computer systems), as one or more programs executed by onone or more controllers (e.g., microcontrollers) as one or more programsexecuted by one or more processors (e.g., microprocessors), as one ofmore field programmable gate arrays (FPGAs), as other firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of ordinary skill in the art in light of theteachings of this disclosure.

When logic is implemented as software and stored in memory, logic orinformation can be stored on any physical computer-readable medium foruse by or in connection with any processor-related system or method. Inthe context of this disclosure, a memory is a computer-readable mediumthat is an electronic, magnetic, optical, or other physical device ormeans that contains or stores a computer and/or processor program. Logicand/or the information can be embodied in any computer-readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions associated with logic and/or information.

In the context of this specification, a “computer-readable medium” canbe any physical element that can store the program associated with logicand/or information for use by or in connection with the instructionexecution system, apparatus, and/or device. The computer-readable mediumcan be, for example, but is not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatusor device. More specific examples (a non-exhaustive list) of thecomputer readable medium would include the following: a portablecomputer diskette (magnetic, compact flash card, secure digital, or thelike), a random access memory (RAM), a read-only memory (ROM), anerasable programmable read-only memory (EPROM, EEPROM, or Flash memory),a portable compact disc read-only memory (CDROM), digital tape.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet, including but not limited to U.S. Pat. No. 5,893,363 and U.S.Pat. No. 7,604,596 are incorporated herein by reference, in theirentirety. Aspects of the embodiments can be modified, if necessary, toemploy systems, circuits and concepts of the various patents,applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

What is claimed is:
 1. An ultrasound system, comprising: a transducerarray including a number of transducer elements configured to produceand transmit ultrasound into a body and produce analog return signalscorresponding to received ultrasound returns from an imaging depth for anumber of channels; an amplifier configured to amplify the analog returnsignals produced by the transducer elements in accordance with a depthdependent amplification function that compensates for attenuation ofultrasound with imaging depth; circuitry for converting the amplifiedanalog return signals into digital return signals for the number ofchannels with a number of analog to digital converters (ADCs) each ofwhich is configured to convert the analog return signals to digitalreturn signals in a number of ranges of depths each of which is lessthan the entire imaging depth; detecting saturation in the ADCs for eachrange of depths by comparing the digital return signals produced by theADCs with one or more thresholds indicative of saturation before thedigital return signals are beamformed; and adjusting the depth dependentamplification function using the comparisons to reduce gain at a rangeof imaging depths which is less than the entire imaging depth from whichthe ultrasound returns are received where saturation is at least one ofencountered, met and exceeded; and a digital signal processor configuredto process the digital return signals.
 2. The ultrasound system of claim1 wherein the circuitry for detecting saturation in the ADCs includes acounter to count occurrences of saturation in the digital return signalsand the circuitry for adjusting the depth dependent amplificationfunction is configured to adjust a gain in the depth dependentamplification function to reduce an occurrence of saturation of thedigital return signals.
 3. The ultrasound system of claim 1 wherein thecircuitry for detecting saturation in the ADCs includes a counter tocount occurrences of saturation in the digital return signals and isconfigured to adjust a gain in the depth dependent amplificationfunction to increase an occurrence of saturation of the digital returnsignals.
 4. The ultrasound system of claim 1 wherein the circuitry fordetecting saturation in the ADCs includes a status bit corresponding toa respective one of each of the plurality of ranges of imaging depthsthat is set if a saturation monitoring threshold value is exceeded atthe corresponding imaging depth.
 5. The ultrasound system of claim 1wherein the circuitry for detecting saturation in the ADCs includes acounter for each of the imaging depth ranges to count occurrences ofsaturation in the digital return signals and is configured to incrementthe respective counter for each of a plurality of ranges of imagingdepths each time a saturation threshold is exceeded for thecorresponding imaging depth range.
 6. The ultrasound system of claim 1wherein the circuitry for detecting saturation in the ADCs includes acommon counter for the imaging depth ranges that is incremented eachtime a saturation monitoring threshold is exceeded at any of the imagingdepth ranges.
 7. The ultrasound system of claim 1 wherein the digitalsignal processor is communicatively coupled to receive a number ofcompensation signals from the circuitry for detecting saturation in theADCs that are indicative of an amount of compensation to compensate forthe adjustment of the gain in the depth dependent amplification functionand includes circuitry that is configured to amplify the digital returnsignals from the front end ASIC by an amount that is based at least inpart on the compensation signals.
 8. The ultrasound system of claim 1wherein saturation monitoring thresholds are based on at least one inputreceived from a user.
 9. The ultrasound system of claim 1 whereincircuitry for detecting saturation in the ADCs includes circuitry forcausing an alert to be provided via a user interface of the ultrasoundimaging system based at least in part on the detected saturated digitalreturn signals.
 10. The ultrasound system of claim 1 wherein thecircuitry for detecting saturation in the ADCs includes circuitry forcausing the ultrasound system to enter a low power state in response toa lack of detected saturation.
 11. An ultrasound system, comprising: atransducer array including a number of transducer elements configured toproduce and transmit ultrasound into a body and produce analog returnsignals corresponding to received ultrasound returns from an imagingdepth in a number of channels; an amplifier configured to amplify theanalog return signals produced by the transducer elements in accordancewith a depth dependent amplification function that compensates forattenuation of ultrasound with imaging depth; a number of analog todigital converters (ADCs) each configured to convert the amplifiedanalog return signals into digital return signals in a number of rangesof imaging depths, each which is less than an entire imaging depth;processing logic programmed to monitor outputs of the ADCs by comparingthe digital return signals from the ADCs for the number of channels withone or more thresholds at a plurality of different imaging depth rangeseach of which is less than the entire imaging depth from which theultrasound returns are received before the digital return signals arebeamformed; and adjust the depth dependent amplification function in arange imaging depths which is less than the entire imaging depth fromwhich the ultrasound returns are received based on the monitored outputsof an ADC associated with the range of depths; and a digital signalprocessor configured to process the digital return signals.
 12. Theultrasound system of claim 11, wherein the processing logic isprogrammed to increase the gain of the depth dependent amplificationfunction in a range of depths, which is less than the entire depth rangefrom which ultrasound returns are received, based on the monitoredoutput of the ADC that converts the analog return signals to digital inthat range.
 13. The ultrasound system of claim 11, wherein theprocessing logic is programmed to decrease the gain of the depthdependent amplification function in a range of depths which is less thanthe entire depth range from which ultrasound returns are received, basedon the monitored output of the ADC that converts the analog returnsignals to digital in that range.
 14. An ultrasound system, comprising:a transducer array including a number of transducer elements configuredto produce and direct ultrasound into a body and to produce analogreturn signals corresponding to received ultrasound returns from animaging depth for a number of channels; an amplifier configured toamplify the analog return signals produced by the transducer elements inaccordance with a depth dependent amplification function thatcompensates for attenuation of ultrasound with imaging depth; a numberof analog to digital converters (ADCs) each configured to convert theamplified analog return signals into digital return signals in a numberof ranges of imaging depths, each of which is less than an entireimaging depth; processing logic configured to monitor outputs of theADCs for the number of channels by comparing the digital return signalsfrom the ADCs for each of the depth ranges with one or more thresholdsbefore the digital return signals are beamformed; and adjust the depthdependent amplification function in a range imaging depths at which ananalog to digital converter converts the analog return signals intodigital return signals; and a digital signal processor configured toprocess the digital return signals.
 15. The ultrasound system of claim14, further comprising a memory that stores a number of times an analogto digital converter produces an output which exceeds a threshold in arange of depths.
 16. An ultrasound system, comprising: a transducerarray including a number of transducer elements configured to produceand direct ultrasound into a body and to produce analog return signalscorresponding to received ultrasound returns from an imaging depth for anumber of channels; an amplifier configured to amplify the analog returnsignals produced by the transducer elements in accordance with a depthdependent amplification function that compensates for attenuation ofultrasound with imaging depth; a number of analog to digital converters(ADCs) each associated with a channel of the ultrasound system andconfigured to convert the amplified analog return signals into digitalreturn signals; and an ADC saturation monitor configured to monitor thedigital return signals from the ADC for each channel by comparing thedigital return signals received for a number depth ranges each of whichis smaller than the entire imaging depth with one or more thresholdsbefore the digital return signals are beamformed; and a register thatrecords whether the digital return signals from an ADC are saturated ineach of the depth ranges; and adjust a gain of the depth dependentamplification function for a range of depths where the digital returnsignals are saturated.